U.S. Pat. No. 9,155,245 discloses a lawn mower that mounts an engine having an engine output shaft caused to project downwards from a lower face of an engine body. This engine is mounted on a mount plate fixed to a pair of left and right main frames. In this, the engine output shaft extends downwards through an opening formed in the mount plate. The opening has a shape sized greater than an output pulley attached to the engine output shaft. The mount plate defines also a plurality of through holes, in addition to the opening. On the top face of the engine body, a fan is provided. Downwardly oriented air current generated by this fan cools the engine. The air current as passing the engine is heated to become hot air current, and a portion of this hot air current passes through the through holes to reach a belt pulley and/or a belt acting as an engine output portion and the hot air current moves further towards the ground surface. Direct contact of such hot air current past the engine with the belt pulley or the belt is undesirable. For, when the lawn mower is performing a lawn mowing operation, this hot air current can damage the lawn.
U.S. Pat. No. 5,284,115 also discloses a lawn mower mounting an engine having an engine output shaft projecting downwards from the lower face of the engine body. The engine is mounted on a plate-like vehicle body frame. In this, the engine output shaft extends downwards through an opening defined in the mounting member. This opening also has a shape sized greater than an output pulley attached to the engine output shaft. In order to inhibit an engine room from becoming a high temperature, hot air current past the engine is discharged via a gap formed between a muffler hood and the vehicle body frame, a gap formed between an engine hood side plate and the vehicle body frame and a gap formed between the engine output shaft and the opening. Below the vehicle body frame, more particularly, below the opening, there is provided a guide plate for guiding hot air current past through the opening sideways. In this lawn mower, as the guide plate is disposed between the vehicle body frame and the engine output pulley, direct collision of the hot air current against the ground surface is suppressed, but a space is required to dispose the guide plate below the opening.